Actuator system with smart load cell

ABSTRACT

The present disclosure includes the use of a smart load cell in a system for controlling an electromechanical actuator. A load cell may be positioned along the outer surface of the electromechanical actuator. Further, the load cell may utilize strain gages and a microcontroller. The load cell may be configured to transmit data to an electric brake actuator controller which includes calibration for operating temperature of the electromechanical actuator.

FIELD

The present disclosure relates generally to aircraft wheel assembliesand, more specifically, to electromechanical actuator systems foraircraft wheel assemblies.

BACKGROUND

Conventional aircraft wheel assemblies comprise rotating and stationarystacks which stop the aircraft when compressed by electromechanicalactuators. Typically, electromechanical actuators are controlled by anelectric brake actuator controller. To properly account for variationsin operating loads on the aircraft brake assemblies, electromechanicalactuators frequently include load cells which provide feedback and aredistinct from and independent of the actuator. These stand-alone loadcells are calibrated manually, by adding individual resistors to theload cells. Such calibration requires significant time, labor, and canonly be performed at actuator assembly time.

SUMMARY

An electromechanical actuator system in accordance with variousembodiments may comprise an actuator and a load cell coupled to theactuator and comprising a circuit board, a strain gauge, amicrocontroller, a bridge, and an output drive circuit in communicationwith the microcontroller. The load cell may comprise two strain gauges.The two strain gauges may be positioned apart from each other atapproximately 180 degrees along a circumference of the outer surface ofthe housing. The load cell may further comprise an output drive circuit.The microcontroller may be positioned between the output drive circuitand a Wheatstone bridge. The output drive circuit may provide a signalto an electric brake actuator controller. The output drive circuit maycomprise a serial interface. The load cell may further comprise a senseresistor in series with the Wheatstone bridge. The load cell may receivea voltage from the electric brake actuator controller.

A method for controlling an electromechanical brake actuator inaccordance with various embodiments may comprise calibrating a load cellof an electromechanical actuator system, wherein the load cell comprisesa flexible circuit board coupled to a housing and having at least onestrain gauge, a microcontroller, a bridge, and an output drive circuitin communication with the microcontroller, and transmitting an outputsignal from the output drive circuit to an electric brake actuatorcontroller. The method may further comprise transmitting a commandsignal from the electric brake actuator controller to anelectromechanical brake actuator. The step of calibrating the load cellmay comprise determining a minimum bridge value at a zero load anddetermining a maximum bridge value at a maximum load. The load cell maybe configured to receive a voltage from the electric brake actuatorcontroller. The output drive circuit may communicate with the electricbrake actuator controller via a serial interface. The load cell mayfurther comprise a sense resistor in series with the bridge.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIG. 1 illustrates a portion of an aircraft brake system in accordancewith various embodiments;

FIG. 2 illustrates a perspective view of an electromechanical brakeactuator housing in accordance with various embodiments;

FIG. 3 illustrates a block diagram of a smart load cell system of anelectromechanical brake actuator system in accordance with variousembodiments; and

FIG. 4 illustrates a flow chart depicting a method of controlling anelectromechanical actuator in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of embodiments herein makes reference to theaccompanying drawings, which show embodiments by way of illustration.While these embodiments are described in sufficient detail to enablethose skilled in the art to practice the inventions, it should beunderstood that other embodiments may be realized and that logical andmechanical changes may be made without departing from the spirit andscope of the inventions. Thus, the detailed description herein ispresented for purposes of illustration only and not for limitation. Forexample, any reference to singular includes plural embodiments, and anyreference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option.

With reference to FIG. 1, a portion of a wheel and brake system 10 isillustrated. Wheel and brake system 10 may comprise, for example, abrake assembly 11. In various embodiments, brake assembly 11 may becoupled to an axle of a wheel 12. For example, brake assembly 11consists of rotors and stators that are compressed together by brakeactuator 36 to reduce the speed of an aircraft.

In various embodiments, brake assembly 11 may comprise a brake stack 27and a brake actuator 36. For example, brake stack 27 may comprisecomponents that interface with both the rotating rotors and the wheelaxle through torque tube 16.

Brake assembly 11 may further comprise, for example, one or more brakeactuators 36. For example, brake actuators 36 may be configured suchthat in response to an operator activating a control (e.g., depressing abrake pedal), brake actuators 36 laterally compress brake stack 27which, in turn, resist rotation of wheel 12 and thus reduces the speedof the aircraft.

Brake actuator 36 may comprise, for example, an electromechanical brakeactuator. In various embodiments, a predetermined level of actuationforce is applied to brake stack 27 by brake actuator 36. In variousembodiments, brake actuator 36 may comprise a hydraulic actuator. Inembodiments where brake actuator 36 is a hydraulic actuator, brakeactuator 36 may be actuated by hydraulic pressure. In furtherembodiments, brake actuator 36 may comprise a hybridelectromechanical-hydraulic actuator. Any type of actuator is within thescope of the present disclosure.

With reference to FIG. 2, in various embodiments, brake actuator 36comprises a brake actuator housing 37. Brake actuator housing 37 maysurround and house at least a portion of the components of brakeactuator 36. Brake actuator housing 37 comprises an outer surface 39. Invarious embodiments, strain gauges that comprise a Wheatstone bridge 200are affixed to outer surface 39 of brake actuator housing 37 to measuretension. For example, outer surface 39 may comprise a channel 41 intowhich Wheatstone bridge 200 may be positioned. Alternatively, Wheatstonebridge 200 may reside internal to brake actuator 36 and measure acompressive load. Any manner of affixing Wheatstone bridge 200 to anypart of brake actuator 36 to measure tension or compressive forces iswithin the scope of the present disclosure.

In various embodiments, Wheatstone bridge 200 comprises a flexibleprinted circuit board 254. In various embodiments, Wheatstone bridge 200comprises two strain gauges 252 positioned apart from one another. Forexample, two strain gauges 252 may be positioned approximately 180degrees from each other along the circumference of outer surface 39 ofbrake actuator housing 37. Although described with reference to specificembodiments, any number and positioning of strain gauges 252 is with thescope of the present disclosure. With reference to FIGS. 2 and 3, asmart load cell 300 is formed by the combination of Wheatstone bridge200, including one or more strain gauges 252, connected (e.g., byflexible printed circuit board 254) and a printed circuit board 38comprising a microcontroller and an output drive circuit.

With reference to FIG. 3, an electrical block diagram of smart load cell300 is illustrated. In various embodiments, data obtained from straingauges 252 may be transmitted from bridge 200 to a signal conditioningcomponent 360. For example, signal conditioning component 360 maycomprise a component configured to make the output of bridge 200suitable for processing by another component of smart load cell 300. Forexample, signal conditioning component 360 may comprise a filter, anamplifier, or any other component capable of conditioning the output ofbridge 200 in a desired manner.

Smart load cell 300 may further comprise, for example, a microcontroller366. Microcontroller 366 may be configured to operate as a dataacquisition and digital signal processing system. For example,microcontroller 366 may receive data from bridge 200 via signalconditioning unit 360. Such data may be processed, stored, and analyzedby microcontroller 366. In various embodiments, microcontroller 366comprises an analog to digital converter 374A, which may be configuredto receive analog data from bridge 200 and convert it to digital datafor processing by microcontroller 366.

After digital signal processing, data may be transmitted frommicrocontroller 366 to an electric brake actuator controller (EBAC) 372.In various embodiments, microcontroller 366 comprises an output drivecircuit. For example, microcontroller 366 may comprise an output drivecircuit 368A which comprises an analog drive circuit 370A. In suchembodiments, microcontroller 366 provides data from a digital analogconverter (within microcontroller 366) to analog drive circuit 370A,which may transmit the analog data to EBAC 372. Analog drive circuit370A may comprise, for example, a 4 milliamp to 20 milliamp drivecircuit.

In various embodiments, microcontroller 366 comprises an output drivecircuit 368B which comprises a digital drive circuit 370B. In suchembodiments, microcontroller 366 provides digital data to EBAC 372. Forexample, digital drive circuit 370B may such utilize a serialcommunication protocol, such as, for example, an RS232 or RS485protocol. Although described with reference to specific embodiments, anymanner of transmitting data from microcontroller 366 to EBAC 372 iswithin the scope of the present disclosure.

Microcontroller 366 may, for example, provide a cleaner and/or moreaccurate output signal to EBAC 372 than an unconditioned analog bridge200 signal. Further, microcontroller 366 may be capable of bidirectionalcommunication with EBAC 372. Bidirectional communication betweenmicrocontroller 366 and EBAC 372 may, for example, allow for built intesting to evaluate the health of EBAC 372 and various sensors,detection and correction of error conditions, among others. Optionally,additional components and/or sensor, such as, for example, anaccelerometer 376, may be added to smart load cell 300 in communicationwith microcontroller 366. For example, accelerometer 376 may allowmicrocontroller 366 to monitor the health and performance of smart loadcell 300, including through the use of built in testing processes.Although described with reference to specific features and components,the use of any component or sensor with smart load cell 300 andmicrocontroller 366 is within the scope of the present disclosure.

Smart load cell 300 may further comprise, for example, a temperaturesensing element 364. In such embodiments, data may be transmitted frombridge 200 to temperature sensing element 364. Temperature sensingelement 364 may transmit data to microcontroller 366. In variousembodiments, data from temperature sensing element 364 may be sent to asignal conditioning component 362 (similar to signal conditioningcomponent 360) prior to microcontroller 366. In various embodiments,microcontroller 366 comprises an analog to digital converter 374B, whichmay be configured to receive analog data from temperature sensingelement 364 and convert it to digital data for processing bymicrocontroller 366.

Further, temperature sensing element 364 may allow microcontroller 366to determine the operating temperature of brake actuator 36 by comparingdata received from bridge 200 to data received from temperature sensingelement 364. In such embodiments, microcontroller 366 may employ atemperature compensation formula to adjust or calibrate data receivedfrom bridge 200 prior to transmitting the data to EBAC 372. During use,the temperature of brake actuator 36 may increase, which can change thecharacteristics of strain gauges 252, which in turn may affect theaccuracy of data provided by strain gauges 252. For example, astemperature increases, strain gauges 252 may expand axially and/orradially, thereby registering a positive strain on brake actuatorhousing 37. Likewise, as temperature decreases, strain gauges 252 maycontract axially and/or radially, thereby registering a negative strainon brake actuator housing 37. Further, resistors and/or other componentsof bridge 200 may fluctuate as temperature increases or decreases.Therefore, determining the temperature of brake actuator 36 and/or brakeactuator housing 37 may be beneficial in correcting and/or calibratingdata received from bridge 200 by microcontroller 366.

In various embodiments, smart load cell 300 may further comprise avoltage reference 358. For example, voltage reference 358 may receivevoltage from EBAC 372. Further, voltage reference 358 may provide afixed voltage to bridge 200 and/or microcontroller 366.

With reference to FIG. 4, a method 400 for controlling anelectromechanical actuator in accordance with various embodiments isillustrated. For example, method 400 may comprise a step 480 ofcalibrating the load cell. For example, step 480 may comprisecalibrating the load cell by determining a minimum bridge value at zeroload and a maximum bridge value at maximum load. In various embodiments,the zero load value may be determined by bridge 200 when brake actuator36 is under no external load (i.e., at rest and at zero extension).Further, the maximum bridge value may be determined by bridge 200 whenbrake actuator 36 is fully extended. The zero load value and the maximumload value may, for example, be transmitted from bridge 200 tomicrocontroller 366.

In various embodiments, the zero load trim value and maximum load trimvalue may be determined at any temperature. For example, the zero loadvalue and maximum load value may be determined at “room” temperature.Room temperature can be defined as the temperature of the surroundingsof the aircraft when the aircraft is not in flight. Variations in theload based on temperature changes are compensated for with temperaturesensing element 364.

Method 400 may further comprise a step 482 of transmitting an outputsignal to an EBAC. For example, microcontroller 366 may transmit asignal through an output drive circuit (such as output drive circuit368A and/or 368B) to EBAC 372. In various embodiments, microcontroller366 may receive data from bridge 200 and adjust or calibrate the datausing a temperature compensation formula. Such data may then betransmitted through the output drive circuit (such as output drivecircuit 368A and/or 368B) to EBAC 372.

In various embodiments, method 400 further comprises a step 484 oftransmitting a command signal from an EBAC. For example, step 484 maycomprise EBAC 372 transmitting a command signal to brake actuator 36. Invarious embodiments, the command signal is calculating using dataprovided to EBAC 372 from smart load cell 300. Specifically, datatransmitted from microcontroller 366 through an output drive circuit(such as output drive circuit 368A and/or 368B) may be used to calculatea command signal, which in turn is transmitted to brake actuator 36. Invarious embodiments, the command signal activates and causes a desireddisplacement of brake actuator 36.

Benefits and other advantages have been described herein with regard tospecific embodiments. Furthermore, the connecting lines shown in thevarious figures contained herein are intended to represent exemplaryfunctional relationships and/or physical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships or physical connections may be present in apractical system. However, the benefits, advantages, solutions toproblems, and any elements that may cause any benefit, advantage, orsolution to occur or become more pronounced are not to be construed ascritical, required, or essential features or elements of the disclosure.The scope of the disclosure is accordingly to be limited by nothingother than the appended claims, in which reference to an element in thesingular is not intended to mean “one and only one” unless explicitly sostated, but rather “one or more.” Moreover, where a phrase similar to“at least one of A, B, or C” is used in the claims, it is intended thatthe phrase be interpreted to mean that A alone may be present in anembodiment, B alone may be present in an embodiment, C alone may bepresent in an embodiment, or that any combination of the elements A, Band C may be present in a single embodiment; for example, A and B, A andC, B and C, or A and B and C.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment,” “an embodiment,” “anexample embodiment,” etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f), unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises,”“comprising,” or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. An electromechanical actuator system, comprising:an actuator having a housing with an outer surface comprising a channel;and a load cell coupled to the actuator, the load cell comprising: acircuit board, a bridge including a strain gauge disposed within thechannel and coupled to the housing of the actuator, the strain gaugeconfigured to measure a strain on the housing of the actuator, amicrocontroller configured to receive data from the bridge, and anoutput drive circuit in communication with the microcontroller.
 2. Theelectromechanical actuator system of claim 1, wherein the load cellfurther comprises a temperature sensing element and the microcontrolleris configured to determine an operating temperature of theelectromechanical actuator system.
 3. The electromechanical actuatorsystem of claim 1, wherein the load cell comprises two strain gauges. 4.The electromechanical actuator system of claim 3, wherein the two straingauges are positioned apart from each other at 180 degrees along acircumference of the outer surface of the housing.
 5. Theelectromechanical actuator system of claim 1, wherein the load cellfurther comprises a temperature sensing element.
 6. Theelectromechanical actuator system of claim 1, wherein the output drivecircuit provides a signal to an electric brake actuator controller. 7.The electromechanical actuator system of claim 1, wherein the actuatorcomprises one of an electromechanical actuator, a hydraulic brakeactuator, and a hybrid brake actuator.
 8. The electromechanical actuatorsystem of claim 1, wherein the load cell further comprises anaccelerometer in communication with the microcontroller.
 9. Theelectromechanical actuator system of claim 1, wherein themicrocontroller and an electromechanical brake controller are inbidirectional communication with each other.
 10. The electromechanicalactuator system of claim 1, wherein the output drive circuit includes ananalog drive circuit and a digital drive circuit.
 11. Theelectromechanical actuator system of claim 10, wherein the analog drivecircuit provides a digital signal to an electric brake actuatorcontroller, and wherein the digital drive circuit provides an analogsignal to the electric brake actuator controller.